The present invention relates to a new and distinct variety of blood nectarine tree, also named red colored flesh nectarine, Prunus persica (L.) Batsch, which has been given the variety denomination ‘NSRED15273’. This new tree produces fruits with a long shelf life without alteration both on the tree after growth completion and after harvesting, very good eating quality, clingstone dark red or blood red flesh fruits for fresh market in August in the Pyrénées-Orientales department, France. Contrast is made to ‘NECTARPERF’ white nectarine tree (U.S. Plant Pat. No. 23,357) to ‘NSRED14262’ blood nectarine tree (U.S. Plant patent application Ser. No. 16/350,460) and to ‘NSRED15270’ blood nectarine tree (U.S. Plant patent application Ser. No. 16/350,466) for reliable description. ‘NSRED15273’ is a promising candidate for commercial success in that it has very attractive fruits with very long shelf life without alteration both before and after harvesting.